The chronic animal model of RLF usually employed by investigators is based upon observing acute proliferative retinal vascular changes in histological preparations of kitten or puppy retinas following long-time (several days) continuous exposure to high levels of oxygen. This model is inefficient since variations in individual response require use of large numbers of animals, statistical analysis of data, and a considerable investment of investigator time. We are developing an acute animal model of RLF in which the change in blood velocity through major retinal arteries resulting from the initial vasoconstriction and capillary closure following onset of hyperoxia is observed by high speed (40 frames per second) infrared fluorescent dye angiography. This earliest response to oxygen is less subject to time mediated perturbations than one which develops over a period of several days or more and is therefore likely to form a more consistent basis for an RLF animal model. A method for non-invasively monitoring percent hemoglobin saturation potentially for use on premature human infants is being investigated. The method applies extant technology in a way that takes into consideration the special circumstances under which the Infant Special Care Unit physicians must work and is designed to provide high temporal data resolution. Interface to the patient is to be made by use of a scleral contact lens connected to a fiber optics cable.